Web Services Composition and Geographic Information - Geographical Information Systems: Trends and Technologies - page 108

W3C Web services

According to the defi nition of the W3C working group (Booth et al. 2004),
a Web service is

'a software system designed to support interoperable machine-
to-machine interaction over a network. Other systems interact
with the Web service in a manner prescribed by its description
using messages, typically conveyed using HTTP with an XML
serialization in conjunction with other Web-related standards.'

Standards are one of the main reasons behind the massive adoption
and deployment of Web services as a means to create a framework for
application-to-application interaction by the Web publication of the business
functionalities and a universal Web access to them. In particular, three
main roles can be associated with the interacting applications, namely the
service provider that owns a Web service and makes it accessible through
the network, the service client which represents a potential user of a Web
service, and fi nally, the service registry corresponding to the entity that
allows service clients to locate the service and obtain information on how to
invoke its functionalities (Yu et al. 2008). Figure 1 illustrates the interaction
among the above-mentioned roles.
Among the advantages offered by the Web services technology the
following can be mentioned (Tsalgatidou and Pilioura 2002):

￿ easy and fast deployment compared to the efforts required to realize
a traditional enterprise application;
￿ interoperability through the adoption of common XML based
standards;

Service
Registry

Client

Interact

Service
Provider

Service
Requestor

Fig. 1. The basic Service Oriented Architecture.